FIGS. 8A and 8B schematically illustrate two major arrangement forms of a drive unit in the rotating electrical machine of the above-described type. More specifically, FIG. 8A shows a control case 1 which houses a drive unit such as an inverter and is separated from a rotating electrical machine 2. An output voltage of the inverter is supplied to the machine 2 via a power supply cable 3 drawn out of the control case 1. This arrangement form necessitates an installation space for the control case 1 aside from one for the machine 2, resulting in a problem of low space efficiency. This arrangement form also has a problem that surge voltage results from reflection of radio waves between the machine 2 and the power supply cable 3 or the like and a problem that radio waves emitted from the power supply cable 3 influences other equipment as noise.
On the other hand, FIG. 8B shows a control case 1′ fixed to an outer periphery of a frame 2a′ of a rotating electrical machine 2′ in the other arrangement form. This arrangement form can achieve a reduction in the installation space while rendering the power supply cable 3 and the like unnecessary, whereupon the aforementioned problem of noise and the like can be overcome.
However, even in a case where an elastic material such as rubber is interposed between the frame 2a′ and the control case 1′ in the latter rotating electrical machine 2′, the control case 1′ resonates with the frame 2a′ as the result of vibration transmission from the frame 2a′ and resultant resonance is produced from the control case 1′. Furthermore, the control case 1′ houses a known switching circuit including electronic components constituting the inverter, a substrate for the mounting of the electronic components and the like. Accordingly, the control case 1′ is rendered relatively larger in size and noise resulting from vibration is also increased, with the result that the electronic components are required to be protected from vibration.
The control case 1′ as shown in FIG. 8B is directed to a rotating electrical machine including a stator frame which is provided with a mass in order that vibration and noise both produced by the rotating electrical machine may be suppressed. However, such a countermeasure is not suggested for the control case 1′. Furthermore, the electronic components of the inverter need to be protected from vibration and accordingly, there is a problem to be overcome when the control case 1′ is attached to the machine 2′.